The overall aim of this research program is to provide a realistic computational model of how neuromodulatory systems act upon cortical and subcortical networks of the human brain, and of how their actions influence normal and addictive modes of behavior in the real world. An integrated systems-level computational approach will be pursued in order to (a) discover and implement anatomical and physiological principles underlying neuromodulatory functions, (b) study their integration with other brain areas and processes, especially those underlying learning and memory, and (c) study the interactions between (internal) neural events and (external) behaviors. In stages of increasing complexity, a detailed neuronal network model of sensory and motor cortical areas, subcortical circuits and neuromodulatory nuclei will be designed and implemented in an autonomous robot. The model will incorporate realistic anatomical and physiological properties and be capable of plastic changes in connectivity depending upon actual sensory experience and behavior. In a first stage, we plan to implement a neuromodulatory system with properties similar to a midbrain dopamine system, producing neural responses that are related to reward and reward predicting stimuli. In addition to this reward system we will implement a separate system responsive to aversive stimuli and investigate possible modes of functional interaction between them. In order to investigate the hypothesized connection between the development of addictive behavior and processes related to memory and learning we will expand the model to include additional cortical and subcortical networks. Our modeling studies will allow us to provide an analysis of the causal roles played by different components of the neural architecture, of pharmacological and physiological properties, of learning and memory and of actual behavior in the switch from normal and controlled modes of behavior to addiction. A comprehensive and detailed embodied (robot) model has the potential of serving as a unique explanatory and predictive tool aiding in future empirical research on drug abuse and addiction.